1. Field of the Invention
The present invention relates to a photographic film processing apparatus for developing photographic films and photographic printing paper exposed to light or radioactive rays, such as x-rays in the medical field, the industrial field and the general industrial fields.
2. Discussion of the Related Art
Generally, when taking an object by using an optical photographic film or a radiographic film, and developing the exposed optical photographic or radiographic film (hereinafter referred to simply as "film") for the examination of the photograph or the radiograph of the object at an early stage after taking the photograph or the radiograph of the object in the medical field, the industrial field and the general industrial fields, processing solutions, such as a developing solution, a fixing solution and a developing-and-fixing solution (hereinafter referred to inclusively as "processing solutions") are contained in separate containers respectively, and the exposed film is immersed in the processing solution contained in the container for developing, the film is transported in air to the next container, and then the film is immersed in the processing solution in the next container for fixing. When a large number of films are processed at a time or when the film processing operation is repeated frequently, tanks each having a comparatively large volume and provided with film conveying means, such as film conveying rollers, are used for containing the processing solutions, and the film is conveyed through the successive tanks for continuous processing.
Generally, the processing vessel or the processing tank for containing a processing solution is opened to the atmosphere to feed a film into and to take out the film from the processing vessel or the processing tank. Accordingly, the properties of the processing solution deteriorate naturally with time due to oxidation that occurs in the surface of the processing solution as well as due to repetitive use. Furthermore, the processing solution wetting the components, such as the conveying rollers, of the processing apparatus solidifies in particles by drying or crystallizes in crystals, and the particles or the crystals damage the film. Accordingly, when processing a film by a conventional photographic film processing method, the properties of the processing solutions must be continuously controlled to replenish the processing containers with the processing solutions or to change the processing solutions at the appropriate time, and the components of the processing apparatus wetted with the processing solutions must be frequently cleaned to remove the particles or the crystals.
However, since such control of the processing solutions and maintenance of the processing apparatus are comparatively troublesome, it often happens that unclear images are formed or images are damaged as a consequence of failure in replenishing the processing tanks, changing the processing solutions or cleaning the components of the processing apparatus at the appropriate time. Since the exhausted processing solutions must be disposed of after dilution and naturalization according to relevant laws and regulations, the disposal of a large quantity of waste processing solution requires much time and large cost. Therefore, there has been a demand for a compact photographic film processing apparatus capable of stably processing films by using a comparatively small quantity of a processing solution and of making cleaning work unnecessary or reducing the frequency of cleaning work.
The inventors of the present invention had continuously made efforts in improving the conventional photographic film processing apparatus to meet the foregoing demand, and previously proposed an improved photographic film processing tank in Japanese Patent Nos. 1773397 and 1773398. This previously proposed photographic film processing tank is provided with a film inlet slit and a film outlet slit which are immersed in water to suppress the deterioration of a processing solution contained in the photographic film processing tank due to oxidation, and to prevent the solidification and crystallization of the ingredients of the processing solution due to drying so that the film will not be damaged by the particles or crystals of the ingredients of the processing solution. The inventors incorporated further improvements into this previously proposed photographic film processing tank and proposed a photographic film processing apparatus capable of stably processing films by using a very small quantity of a processing solution and of doing away with troublesome work for supplying and changing a new processing solution and for cleaning the components in Japanese Patent Application No. Hei 4-1721. This previously proposed photographic film processing apparatus is provided with a water tank, and processing vessels each provided with a film inlet slit and a film outlet slit at the opposite ends thereof, having a flat processing chamber and placed in the water tank. A processing solution is supplied into the flat processing chamber so that the processing solution will flow alternately in laterally opposite directions to wet uniformly a film traveling through the processing chamber for developing.
The inventors of the present invention proposed another photographic film processing apparatus developed by incorporating further improvements into this previously proposed photographic film processing apparatus, and proposed the same in Japanese Patent Application Hei. 6-19462 based on the priority of Japanese Patent Application Nos. Hei 5-143678 and Hei 5-143678 prior to this patent application. This photographic film processing apparatus proposed prior to this patent application comprises a water tank, and a processing unit having processing chambers each of a small volume, placed in the water tank, and provided with film conveying rollers. The processing chambers of this photographic film processing apparatus can be sealed even if only the end surfaces of the film conveying rollers are sliding surfaces, and this photographic film processing apparatus is capable of stably increasing the speed of contact (stirring) of the processing solution with the film, of suppressing power consumption and of stably, continuously and quickly carrying out uniform processing by using a very small quantity of the processing solution.
The photographic film processing apparatus proposed in a related patent application is shown in FIGS. 8(a) and 8(b) by way of example. Referring to FIGS. 8(a) and 8(b), the photographic film processing apparatus has a water tank 1, and three processing vessels 32 each having a processing chamber 32a of a small volume and arranged in the water tank 1 along a film conveying direction in which a film F is conveyed. The processing chamber 32a of each processing vessel 32 is defined by disposing two pairs of film conveying rollers 33 and 33' with a given small interval therebetween, closing the space between the top film conveying rollers 33 of the two pairs of film conveying rollers 33 and 33' and the space between the bottom film conveying rollers 33' of the same by a pair of sealing rollers 34 and 34', and placing a pair of support plates 35 and 35' close to the opposite ends of the two pairs of film conveying rollers 33 and 33' and the pair of sealing rollers 34 and 34'. All the processing vessels 32 are supported on the pair of support plates 35 and 35'.
Each processing vessel 32 is immersed in fresh water W contained in the water tank 31 and, as shown in FIG. 8(b), a sectional view taken on line A--A in FIG. 8(a), has an inlet port 35a and an outlet port 35a'. The inlet port 35a and the outlet port 35a' of each processing vessel 32 are connected by tubes 38 to a liquid circulating pump 40 to form a closed circuit, and a small air vent tank 39 is connected to the tube 38. A film guide 36 having a flat slit 36a is placed in the processing chamber 32a of each processing vessel 32. The film conveyor rollers 33 and 33' are driven for synchronous rotation by a driving spur gear 41 driven for rotation about an axis P by a geared motor 42. A film guide 37 and a duct 43 are disposed on the inlet side and the outlet side, respectively, of the processing unit. Thus, the liquid chambers 32a are sealed in a liquid-tight fashion, and the film F is conveyed through the processing vessels 32 along a U-shaped film conveying path.
In this photographic film processing apparatus proposed in the related patent application, a developing solution and a fixing solution are circulated through the first processing vessel 32 and the second processing vessel 32 respectively, fresh water W is circulated through the third processing vessel 32, hot air is blown into the duct 43, and then a film F is passed along the U-shaped path through the processing chambers 32a of the processing vessels 32 for successive developing, fixing, washing and drying.
Although the photographic film processing apparatus of the prior patent applications (Japanese Patent Application Nos. 5-143678 and 6-19462) has the aforesaid excellent effects in processing x-ray films and monochromatic films, it was found through minute examination of the photographic film developing apparatus that the following problems to be solved arise in the photographic film processing apparatus when processing superhigh-speed monochromatic films or color films and when processing long normal-speed films at an increased processing speed.
For example, screen films, i.e., normal-speed films using an intensifying screen, which are used generally for x-ray photography in the medical field, require substantially equal times respectively for developing and fixing. Therefore the time ratio between the developing process and the fixing process is 1:1 and the screen films can be processed continuously for developing and fixing.
Nonscreen films, i.e., superhigh-speed films not using any intensifying screen, which have been generally used in the industrial field and have been widely used in recent years for dental x-ray photography at a low exposure, require a fixing time longer than a developing time to increase the quantity of silver, and the time ratio between the developing process and the fixing process is 1:1.5 or above. When continuously processing such a superhigh-speed film by the conventional method, the time ratio between the developing process and the fixing process is 1:1 based on the time required for fixing. If it is desired to process the superhigh-speed film on the basis of the developing time, the time necessary for the superhigh-speed film to pass through the fixing solution must be 1.5 times the time necessary for the same to pass through the developing solution or longer.
The photographic film processing apparatus of the prior 10 patent application conveys the film through the processing vessels of the same length in the same time. Therefore, the fixing solution must be circulated through the second processing vessel at a velocity higher than that at which the developing solution is circulated through the first processing vessel or the respective concentrations of the developing solution and the fixing solution must be adjusted so that the respective speeds of the developing reaction and the fixing reaction are different from each other to process the superhigh-speed film continuously at an increased conveying speed in a reduced time. Similarly, when processing a long normal-speed film, the respective flow speeds and the respective concentrations of the processing solutions circulated through the processing vessels must be adjusted so as to promote the developing reaction and the fixing reaction to reduce the time in which all the length of the long film passes the photographic film processing apparatus by increasing the film conveying speed.
However, when the flow speed of the processing solution is increased, the flow passage resistance increases progressively and power necessary for circulating the processing solution increases accordingly. Furthermore, since the speed of reaction between the processing solution and the photosensitive layer coating the surface of the film is not necessarily promoted in proportion to the concentration and the flow speed of the processing solution even if the concentration and the flow speed of the processing solution are increased beyond fixed limits respectively, the increase of the concentration and the flow speed of the processing solution beyond the limits is useless. Consequently, when processing the superhigh-speed film, the concentration or the flow speed of the developing solution circulated through the first processing vessel must be reduced, which determines a low rate of process. The increase of the speed of conveying the long normal-speed film is limited for the same reason and hence it is difficult to reduce the processing time.
When processing a color film through a series of steps of coupling, stopping, hardening, washing, bleaching, washing, fixing and final washing, washing steps are essential steps between the specific processes. When processing a film by the photographic film processing apparatus of the prior patent application, the film processed by the processing solution flowing through the processing chamber of the processing vessel travels through the water contained in the water tank, and then the film travels into the processing chamber of the next processing vessel and hence the film is washed after being processed in each processing vessel. Therefore, monochromatic films can be processed by the photographic film processing apparatus of the prior patent application without any problem. However, color films are difficult to be stably processed by the photographic film processing apparatus of the related patent application.
Furthermore, when processing a film by the photographic film processing apparatus of the related patent application, in which the film travels from one processing vessel to the subsequent processing vessel through the water contained in the water tank, when the photographic film processing apparatus is operated in a daylight room, the open upper end of the water tank must be covered closely with a hood or the like to shield the water tank perfectly from light in order that the film may not be exposed to light, which is an obstruction to the ease of operation and the formation of the photographic film processing apparatus in a compact construction. In this respect, the photographic film processing apparatus of the related patent application needs improvements.